Web Performance Audit Skill for Claude

Web performance audits with Core Web Vitals, bottleneck identification, optimization recommendations. Use for page load times, performance reviews, UX optimization, or encountering LCP, FID, CLS issues, resource blocking, render delays.

641 tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

202

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/secondsky/claude-skills --skill web-performance-audit

The instruction itself

10 sections, as written by the author

Web Performance Audit

Conduct comprehensive performance audits and implement optimizations.

Core Web Vitals Targets

|--------|------|-------------------|------|

| LCP (Largest Contentful Paint) | <2.5s | 2.5-4s | >4s |

| FID (First Input Delay) | <100ms | 100-300ms | >300ms |

| CLS (Cumulative Layout Shift) | <0.1 | 0.1-0.25 | >0.25 |

| INP (Interaction to Next Paint) | <200ms | 200-500ms | >500ms |

Performance Measurement

// Using web-vitals library
import { getCLS, getFID, getLCP, getTTFB } from 'web-vitals';

function sendToAnalytics({ name, value, id }) {
  console.log({ name, value, id });
}

getCLS(sendToAnalytics);
getFID(sendToAnalytics);
getLCP(sendToAnalytics);
getTTFB(sendToAnalytics);

Lighthouse Automation

const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');

async function runAudit(url) {
  const chrome = await chromeLauncher.launch({ chromeFlags: ['--headless'] });
  const result = await lighthouse(url, {
    port: chrome.port,
    onlyCategories: ['performance']
  });

  await chrome.kill();
  return result.lhr;
}

Optimization Strategies

Quick Wins (1-2 days)

Enable gzip/brotli compression
Minify CSS/JS
Defer non-critical scripts
Optimize images (WebP, lazy loading)

Medium Effort (1-2 weeks)

Implement code splitting
Add service worker caching
Preload critical resources
Eliminate render-blocking resources

Long-term (1-3 months)

Architecture improvements
CDN optimization
Database query optimization

Performance Budget

{
  "timings": [
    { "metric": "first-contentful-paint", "budget": 1500 },
    { "metric": "largest-contentful-paint", "budget": 2500 }
  ],
  "resourceSizes": [
    { "resourceType": "script", "budget": 150 },
    { "resourceType": "image", "budget": 300 }
  ]
}

Audit Checklist

[ ] Measure baseline Core Web Vitals
[ ] Run Lighthouse audit (mobile & desktop)
[ ] Analyze real user metrics (RUM)
[ ] Identify largest contentful element
[ ] Check for layout shifts
[ ] Review JavaScript bundle size
[ ] Test on slow 3G connection
[ ] Set performance budget
[ ] Configure monitoring alerts

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How to use it

Copy the folder

Take secondsky/web-performance-audit from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.